[Eeglablist] Help with EEG channel location import, channel numbers incorrect

[Maria Fini]

Hello Community,
I am new to eeglab and having some trouble with importing my recorded
electrode locations.
I recorded 64 channels of data using the brainvision EEG recording system,
with electrodes in the standard 10-20 locations, except 1 electrode, which
I removed to do ultrasound stimulation, and placed on the chest to record
HR.
Electrode montage matches that of the template file
('[eeglabPath]/plugins/dipfit2.3/standard_BEM/elec/standard_1005.elc')
with the reference at the left mastoid and the ground front and center on
the cap.

I recorded each subjects' electrode locations using the brainvision
captrack system.
When I go into the gui edit>channel locations> then click 'Read locations'
to bring in the.spf file, the 3d plot of the electrode locations looks
correct, but I am running into a couple of problems: (an pointers would be
greatly appreciated)!

1) Main problem I'm having is that the channel locations look correct in
space, but are registering with different channel numbers than the default
locations, which I am 99% sure is how my data was recorded. Ie electrode
Fp1 in the default template, and I believe also in my recording, is
registered as channel 1 in the EEG data, but when I load in my recorded
locations, it shows up as channel 43, so the data and electrode assignments
are getting shuffled into wrong positions in the eeg data matrix (see
attached photo 3: template locations on the right, left is data after .spf
channel location file loaded). I think the program is assigning them
numbers 1-64 based on what order the electrodes were detected by the cap
track system, because usually the algorithm starts by the left ear. Yet,
the locations in 3d space are correct.

2) Secondary problem is that the electrode which I removed from the cap for
the ultrasound and used to record the heart rate, was also removed from the
captrack file. I don't really want this electrode included in the global
scalp calculations because it was used to record HR, not EEG. It seems I
have to manually enter it back in to prevent an error in the system from
having less electrode locations than recorded channels. I can manually do
this using the coordinates of the reference, but it's a pain.  This channel
seems to get rejected in cleanline, so I guess it isn't too much of a
problem.


 I suppose I could just go forward on my data processing with the default
locations, but I figured since I recorded the actual electrode locations, I
might as well use them. Any suggestions on how to still use the recorded
locations, but not screw up the channel numbers would be wonderful!
Thanks for your time.


-- 
Maria Fini
Arizona State University
Tyler Neuroperformance Lab, Dept. of Biomedical Engineering
PhD Student
*703.989.9650*
*mfini at asu.edu <mfini at asu.edu>*